Hydrated rice has been produced conventionally by immersing raw rice in water or hot water for a long period of time. However, the water absorption of conventional hydrated rice is insufficient, so that a relatively larger amount of water has been needed for cooking such rice or preparing fried rice. It is disadvantageous that tasty cooked rice, being overall soft but having a slightly hard surface, cannot be obtained for a short time when a greater amount of water is added prior to heating. This represents how difficult it is to determine an appropriate amount of water, specifically that it is extremely difficult to constantly prepare homogeneous and tasty products although a package of such product for one meal is small in volume.
Furthermore, for producing rice balls and the like by using molds, conventionally, rice is once steam-boiled and prepared into .alpha. type, which is then packaged into molds followed by molding under pressure and heating over direct flame to prepare baked rice balls and the like.
However, rice completely prepared into .alpha. type is already in the form of boiled rice, where the grains stick together due to the Starch on the surface, and the rice is packed in molds with much difficulty, and the continuous mechanical production of a greater amount of rice balls is very difficult, which induces troublesome works in machine washing and is expensive. In case that the rice prepared into the form of boiled rice is molded under pressure, the grains get mashed if the rice is too strongly compressed and the products if gently steamed again lose the shape immediately, so that such rice has a disadvantage in that the rice cannot be processed widely other than in the form of baked rice balls.